textproduct: Quad Cities

KEY MESSAGES

- Hot and humid conditions through Saturday, with afternoon heat indices in the mid 90s to around 100F.

- Isolated to scattered showers and storms through Saturday largely diurnally driven with Friday PM favored for the better coverage (30-50%), although Saturday coverage may rival in the late afternoon/evening along a cool front.

- Wildfire smoke will be found in our skies into the weekend. This looks to be mostly aloft resulting in hazy skies at times, however thicker concentrations near surface and unhealthy air quality is possible across parts of northern Illinois through tonight.

- Pattern change next week will bring periodic storm chances and cooler temperatures.

SHORT TERM /THROUGH TONIGHT/

Issued at 300 AM CDT Thu Jul 16 2026

Light winds, abundant low level moisture and radiational cooling will bring the potential for some fog again early this morning, mainly in the river valleys and nearby areas. This should dissipate by around 8 AM.

There are signs of change in this dry and hot pattern, and initially this begins with the return of shower and storm chances today. These chances are low (15-30%) and a result of weak forcing with a lake enhanced front possibly washing out near the U.S. Hwy 20 to Hwy 30 corridor in IL today. While a moisture-rich environment (PWAT values 1.8 to 2 inches) and weak forcing from a remnant upper low encroach from the south.

The weak backdoor front could aid in getting the wildfire smoke closer to the surface into parts of northern Illinois, which could contribute to unhealthy air quality and an Air Quality Alert remains in effect for Jo Daviess and Stephenson counties through this evening. The HRRR shows high near surface smoke concentrations meandering into NW Illinois at times today and again later tonight through Friday. With this in mind, folks in N Illinois and nearby areas of eastern Iowa are encouraged to monitor air quality, particularly if you're sensitive to air pollution and plan to be outdoors. Monitor for any changes to Air Quality Alerts.

Otherwise, today is another day of similar heat and humidity with highs mainly around 90 to the lower 90s and PM peak heat index readings from the mid 90s to around 100F. Some localized higher readings over 100F will be possible.

Tonight, any isolated shower or storms should dissipate with the loss of heating leaving behind another warm, muggy night with lows around 70 to the lower 70s.

LONG TERM /FRIDAY THROUGH WEDNESDAY/

Issued at 300 AM CDT Thu Jul 16 2026

Shower and storm chances will increase a bit (20-50%) on Friday as the moisture-rich airmass (PWATs 1.8 to 2 inches) overspreads the area while weak forcing lingers attendant to the remnant upper low. The peak coverage is expected in the afternoon with the activity gradually waning with the loss of heating Friday night. Modest instability could support a couple of stronger storms with potential for gusty winds with precip loading or cell collapse, but limited vertical wind shear should keep the threat for severe very low. Slow storm motions and large warm cloud layer depths supporting high rainfall rates of 1-2"/hr will lead to the potential for localized heavy rain. The scattered convection could alleviate the heat for some, otherwise it will be another day of highs around 90 or lower 90s and with some higher dew points the potential could exist for more widespread heat index readings around 100 or possibly a little higher, although clouds and convection will play a factor for just how hot it gets.

Saturday, the signal is increasing for a cold front arriving in the late afternoon and evening accompanied by storm chances. PoPs are currently 20-30%, greatest in our eastern counties, but given the signal for a bit more frontal convergence and the lingering very moist airmass, I believe the PoPs may need to get pushed up more (30-50%) coverage area-wide. Stronger deep layer shear aided by a strengthening Great Lakes jet may foster the potential for at least isolated severe storms with damaging winds the primary threat. Currently the stronger shear is east of the Mississippi and that is the area where the Storm Prediction Center has placed a Level 1 out of 5, or Marginal risk for severe weather Saturday PM. Similar to Friday, with the high moisture content heat index readings could be more widespread around 100 or a bit higher.

The front will pass through Saturday night and high pressure will bring some slight cooling for Sunday with highs mainly in the mid to upper 80s, with a few areas southwest still around 90.

The pattern is set to undergo a change toward broad eastern troughing and western ridging over the weekend into next week. A series of shortwaves or ridge riders on the edge of the "ring of fire" out west should result in periodic storm chances. Can't rule out some severe threat at times in the northwest flow aloft, but plenty of uncertainties in timing/strength/ location of these waves at this range. What is of higher confidence is a return to cooler/seasonable temperatures next week with the Climate Prediction Center (CPC) latest 6-10 day outlook showing some signal (30-40%) for leaning below normal July 21-25.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 555 AM CDT Thu Jul 16 2026

Patchy fog mainly in river valleys and nearby areas will dissipate by 13z. Thereafter, predominantly VFR conditions are expected with scattered to broken diurnal cumulus (4-5kft agl). A shower or storm is possible mainly from 18z to 01z, but coverage looks to be sparse (20% or less) and therefore confidence is too low for any mention at this time. Can't rule out some patchy fog again late tonight, but this also appears too limited for any mention.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...Air Quality Alert until midnight CDT tonight for ILZ001-002. MO...None.